U.S. patent number 7,536,956 [Application Number 10/536,468] was granted by the patent office on 2009-05-26 for linear shaped charge system.
This patent grant is currently assigned to Rapid Entry Pty Limited. Invention is credited to Scott Allman, Chris Murray, James Sammons.
United States Patent |
7,536,956 |
Sammons , et al. |
May 26, 2009 |
Linear shaped charge system
Abstract
An elongate explosive charge element (25), said explosive charge
element (25) including a flexible frangible cutting sheet (26) and
an explosive agent (27) said charge element (25) adapted to the
penetration of a barrier structure.
Inventors: |
Sammons; James (Hendra,
AU), Murray; Chris (Bronte, AU), Allman;
Scott (Peakhurst, AU) |
Assignee: |
Rapid Entry Pty Limited
(Peakhurst, AU)
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Family
ID: |
29741595 |
Appl.
No.: |
10/536,468 |
Filed: |
November 28, 2003 |
PCT
Filed: |
November 28, 2003 |
PCT No.: |
PCT/AU03/01585 |
371(c)(1),(2),(4) Date: |
March 27, 2006 |
PCT
Pub. No.: |
WO2004/048880 |
PCT
Pub. Date: |
June 10, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060201373 A1 |
Sep 14, 2006 |
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Foreign Application Priority Data
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Nov 28, 2002 [AU] |
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2002952984 |
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Current U.S.
Class: |
102/476; 89/1.14;
102/309; 102/307; 102/306 |
Current CPC
Class: |
F42B
1/036 (20130101); C06C 5/04 (20130101); F42B
3/08 (20130101); F42B 1/024 (20130101); C06B
45/00 (20130101); F42B 1/032 (20130101); F42B
1/028 (20130101) |
Current International
Class: |
F42B
12/00 (20060101) |
Field of
Search: |
;102/306,307,476,309
;89/1.14 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 669 723 |
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May 1992 |
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FR |
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2 148 463 |
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May 1985 |
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GB |
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2 176 878 |
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Jan 1987 |
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GB |
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Other References
English Abstract of FR 2 669 723 dated May 29, 1992. cited by
other.
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Primary Examiner: Eldred; J. W
Assistant Examiner: Klein; Gabriel J
Attorney, Agent or Firm: Ladas and Parry LLP
Claims
The invention claimed is:
1. A flexible linear charge element adapted to the penetration of a
structure; said linear charge element forming an elongate composite
structure; said composite structure including: (a) an extruded
carcass of closed cell foam; (b) a first overlaid layer of a
cutting sheet liner component, said first overlaid portion
overlaying and abutting said carcass; (c) a second overlaid layer
of explosive sheet, said second overlaid layer overlaying and
abutting said first overlaid layer; and (d) a third overlaid layer
of an inertial mass tamping cararpace, said third overlaid portion
overlaying and abutting said second overlaid portion, wherein said
carcass is provided with side flange portions; said side flange
portions providing termination elements for said first, second and
third layers; each of said first, second and third layers being
affixed to said carcass by a suitable adhesive such that each of
said first, second and third layers abut said side flange portions;
said inertial mass cararpace comrprising a dense, non-toxic,
flexible plasticized metal composite.
2. The liner charge element of claim 1 wherein said cutting sheet
liner component is disposed between said layer of explosive sheet
and said extruded carcass.
3. The linear charge element of claim 2 wherein said cutting sheet
liner component comprises a matrix of polymers incorporating a
dense distribution of metal carbide particles.
4. The linear charge element of claim 1 wherein said layer of
explosive sheet is a shaped charge component; a shape of said
shaped charge component adapted to produce a "Monroe Effect" when
detonated.
5. The linear charge element of claim 1 wherein said inertial mass
tampering carapace is formed of a dense inert compound.
6. The linear charge element of claim 5 wherein said inert compound
comprises powdered barium sulphate.
7. The linear charge element of claim 1 wherein said stand-off
member component is adapted to provide a separation between said
cutting sheet liner and said structure.
8. The linear charge element of claim 7 wherein said extruded
carcass is in the form of an elongate flexible closed cell foam
structure.
9. The charge element of claim 7 wherein said extruded carcass is
in the form of an elongate flexible hollow tubular member.
10. The linear charge element of claim 1 wherein said composite
structure is provided with attachment means adapted to attach said
linear charge element to a surface of said structure.
11. The charge element of claim 10 wherein said attachment means
comprises at least one adhesive strip arranged along an underside
of said composite structure.
12. The linear charge element of claim 11 wherein said attachment
means comprises at least one magnetic strip arranged along an
underside of said composite structure.
Description
The present invention relates to systems and methods adapted to
shaped charge systems for the controlled application of a
destructive explosive charge and, more particularly for the gaining
of forced entry into buildings and structures in situations where
such entry is required for military or law enforcement purposes and
where such entry is denied.
BACKGROUND
In both military and law enforcement operations it may become
necessary to gain forced entry into buildings where such entry by
normal means is denied. Some examples of such situations may
include the rescue of hostages or the interdiction of serious
criminal activity. In such situations the more conventional means
of forced entry by the use of rams or sledge hammers and the like
may be rendered ineffective by the particular structural or
barricaded entry conditions of the building.
In such situations the only recourse may be to use explosive entry
techniques. These are high risk operations, with known methods
making use of metal fragments to effect penetration at the desired
point of entry, with risk of injury to the occupants of the
building, or even of the operational personnel.
Numerous forms of linear shaped charges may be employed for these
purposes as well as for a range of civil applications, particularly
in controlled demolition work. Known systems suffer from a number
of shortcomings depending on the particular application and the
type of charge system. Thus those systems which employ rigid metal
liners cannot be applied to curved surfaces and the metal ejecta
generated by the liner presents a danger to personnel. Malleable
linear charges are known but only allow relatively limited
bending.
It is an object of the present invention to offer systems of forced
entry using explosive means in which the explosive effect is
limited to an extremely short range, or otherwise addresses or
ameliorates the above disadvantages.
BRIEF DESCRIPTION OF INVENTION
Accordingly, in one broad form of the invention, there is provided
an elongate explosive charge element, said explosive charge element
including a flexible frangible cutting sheet, said charge element
adapted to the penetration of a barrier structure.
Preferably the charge element of said cutting sheet is comprised of
a matrix of polymers including plasticisers, stabilizers and
flexible agents, said matrix containing a substantially uniform
distribution of powdered material.
Preferably the charge element of said powdered material is selected
singly or in combination from a group of metals and ceramics, said
group of metals including copper, aluminium, brass and ferrous
metals.
Preferably said cutting sheet is formed by an extrusion
process.
Preferably the charge element of said cutting sheet is formed by a
casting process.
Preferably the charge element of said cutting sheet is associated
with an explosive agent.
Preferably said explosive agent is in sheet form laminated to said
cutting sheet, the lamination comprising an explosive agent layer
and a first cutting sheet layer.
Preferably said lamination of said cutting sheet and said explosive
agent layer are formed so as to produce a shaped charge effect when
combined with a stand-off material; said charge effect having the
general behavioral characteristics of the "Monroe Effect".
Preferably said lamination of said first cutting sheet and said
explosive agent layer is combined with a second layer of cutting
sheet so as to substantially envelop said explosive agent layer and
said first cutting sheet; said second layer acting as a tamping
layer.
Accordingly, in a further broad form of the invention, there is
provided an elongate explosive charge element, said explosive
charge element including a flexible frangible explosive cutting
sheet, said charge element adapted to the penetration of a barrier
structure.
Preferably said explosive cutting sheet is comprised of a matrix of
polymers including plasticisers, stabilizers and flexible agents,
said matrix containing a substantially uniform distribution of
powdered material, said matrix further containing a distribution of
explosive agent.
Preferably said powdered material is selected singly or in
combination from a group of metals and ceramics, said group of
metals including copper, aluminium, brass and ferrous metals.
Preferably said explosive cutting sheet is formed by an extrusion
process.
Preferably said explosive cutting sheet is formed by a casting
process.
Preferably said explosive cutting sheet is formed so as to produce
a shaped charge effect when combined with a stand-off material;
said charge effect having the general behavioral characteristics of
the "Monroe Effect".
Preferably said explosive cutting sheet and said stand-off material
is combined with a layer of flexible frangible cutting sheet, said
flexible frangible cutting sheet acting as a tamping layer.
Preferably said charge element is provided with a metal liner.
Preferably said metal liner is combined with laminations of said
flexible frangible cutting sheet and said explosive agent; said
metal liner acting a penetrating agent; said cutting sheet acting
as a tamping agent.
Preferably said laminations of said cutting sheet, said explosive
agent and said liner, when combined with a stand-off material act
as a shaped charge with the behavioral characteristics of the
"Monroe Effect".
Preferably said metal liner is combined with laminations of said
flexible frangible explosive cutting sheet; said metal liner acting
as a penetrating agent; said explosive cutting sheet acting as a
tamping agent.
Accordingly, in a further broad form of the invention, there is
provided a charge carrier adapted to support elongate explosive
charge elements, said charge carrier adapted to the penetration of
a masonry wall.
Preferably said carrier is comprised of a frame having a generally
rectangular perimeter and at least one cross member, the members of
said frame and cross member formed of hollow section polymeric
material.
Preferably said frame members have an outer face provided with a
channel extending the length of said members; said channel adapted
to accept said elongate explosive charge element as an insert.
Preferably said frame perimeter and said cross member form a sealed
container adapted for the retention of a tamping fluid; said sealed
container provided with apertures and closure means for the filling
of said tamping fluid.
Preferably the internal surfaces of said sealed container are
pre-coated with a gelling agent adapted to modify said tamping
fluid into a tamping gel when said fluid is added to said
container.
Preferably said frame is provided with foot elements adapted to
provide a height adjustment facility to said perimeter frame.
Preferably said frame is provided with an adjustable hinged support
brace, said brace attaching to the rear face of a cross member.
Preferably said frame is provided with a plurality of charge ports
on the rear face of said frame members.
Preferably said elongate explosive charge element is a composite
layered and shaped assembly of flexible frangible cutting sheet and
an explosive agent.
Preferably said elongate explosive charge element is a composite
layered and shaped assembly of flexible frangible explosive cutting
sheet and an explosive agent.
Preferably said explosive charge element includes a shaped metal
liner.
Accordingly, in a further broad form of the invention, there is
provided a charge carrier adapted to support an elongate explosive
charge element adapted to effect a directed explosive charge for
the penetration of a barrier in which the penetrating agent is a
fluid.
Preferably said barrier is comprised of structures including
domestic and commercial metal roller doors, metal doors, fire
doors, reinforced timber doors and glass doors.
Preferably said carrier is comprised of an elongate body of hollow
section polymeric material.
Preferably said elongate body is provided with a sealing end cap at
a first end and filler end cap at a second end.
Preferably said filler end cap is provided with an aperture and
closure means adapted to allow the filling of said body with a
tamping fluid.
Preferably said filler end cap is provided with a detonating cord
grommet.
Preferably the internal walls of said body are pre-coated with a
gelling agent adapted to modify said tamping fluid into a tamping
gel when said fluid is added to said body.
Preferably said elongate body is provided with an adjustable foot
element adapted to provide a height adjustment facility to said
body.
Preferably said elongate body is provided with an adjustable hinged
brace.
Preferably said body is provided with flexible magnetic strips
disposed along portions of the front face of said body, said strips
adapted to attach said charge carrier to a ferrous metal
surface.
Preferably said elongate body is provided with internal guide rails
adapted to accept a loading card as a friction sliding fit.
Preferably said loading card is an elongate polymeric extrusion
having front and rear wall elements separated by transverse
dividing elements so as to form a number of longitudinal passages
through the length of said card.
Preferably said loading card is provided with a series of slots and
holes disposed at each end of said card adapted to accept and
retain a winding of detonating cord laid along the front face of
said card so as to form an explosive charge element.
Preferably said explosive charge element is combined with a
flexible frangible cutting sheet.
Preferably said explosive charge element comprises a frangible
cutting sheet, the matrix of said cutting sheet containing a
distributed explosive agent.
Accordingly, in a further broad form of the invention, there is
provided a method for the penetration of a barrier structure, said
method including the steps of, a. forming a flexible frangible
cutting sheet by a process of extruding or casting in a suitable
mould, a mixture of polymers including plasticisers, stabilizers,
flexible agents and powdered metal or ceramics, b. shaping said
cutting sheet in combination with a layer of explosive agent and a
stand-off material to form an elongate explosive charge element, c.
placing said explosive charge element in contact with said barrier
structure and detonating said explosive charge element.
Accordingly, in a further broad form of the invention, there is
provide a method for the penetration of a barrier structure, said
method including the steps of. a. forming a flexible frangible
explosive cutting sheet by a process of extruding or casting in a
suitable mould, a mixture of polymers including plasticisers,
stabilizers and flexible agents, powdered metal or ceramics and an
explosive agent, b. shaping said explosive cutting sheet and
combining said sheet with a stand-off material to form an elongate
explosive charge element, c. placing said explosive charge element
in contact with said barrier structure and detonating said
explosive charge element.
Accordingly, in a further broad form of the invention, there is
provided a method for the penetration of a barrier structure using
a charge carrier, said method including the steps of, a. installing
an elongate explosive charge element in said charge carrier, b.
filling said charge carrier with a tamping agent, c. placing said
charge carrier in contact with said barrier structure and
detonating said explosive charge element.
Accordingly, in a further broad form of the invention, there is
provided a flexible linear charge system comprising elongate
elements; said elements including a malleable explosive charge
element, a liner and a stand-off member enveloped in a flexible
elongate inertial mass carapace.
Preferably said malleable explosive charge element is comprised of
flexible sheet explosive shaped so as to produce jetting of said
liner when detonated.
Preferably said jetting produces a "Monroe Effect".
Preferably said liner is a composite of an extruded matrix
containing a dense distribution of solid particulate matter.
Preferably said solid particulate matter is a dense metal
carbide.
Preferably said solid particulate matter is any plasticized
metal.
Preferably said stand-off member is comprised of closed-cell
plastic foam.
Preferably said stand-off member is comprised of an extruded
polymeric tube.
Preferably said inertial mass carapace is comprised of an extruded
compound of a metallic powder and plasticizer.
Preferably said inertial mass carapace is adapted to substantially
envelop said elongate elements leaving at least an exposed portion
along that side of said stand-off member opposite said explosive
charge element.
Preferably said inertial mass carapace is formed with flat surfaces
adjoining each side of said at least an exposed portion; said flat
surfaces provided with attachment means for attachment to a surface
to which said linear charge system is to be applied.
Preferably said attachment means are self-adhesive strips.
Preferably said attachment means are magnetic strips attached to
said flat surfaces.
Preferably bungs are adapted to close off open ends of said
extruded polymeric tube so as to allow retention of a fluid
therein.
Preferably at least one of said bungs is provided with one-way
valve means adapted to the passage of said fluid into said extruded
polymeric tube.
Preferably said fluid is a pressurized gas.
Accordingly, in a further broad form of the invention, there is
provided a flexible linear charge element comprising an extruded
closed cell carcass provided with a central aperture; said carcass
having an upper arcuate surface and a lower flat surface and
laterally extending flange portions; said arcuate surface overlaid
by a first layer composed of a frangible liner material.
Preferably said first layer is overlaid by a second layer
comprising an explosive sheet.
Preferably said first layer is overlaid by a second layer
comprising an inertial mass carapace.
Preferably said flat surface is provided with an adhesive
layer.
Accordingly, in a further broad form of the invention, there is
provided a linear charge carrier element comprising a length of a
section of plastic tube having an outer surface to which is affixed
an inner surface of a first layer comprising explosive sheet
material and wherein a second layer of suitable fibrous material is
affixed to an outer surface of said explosive sheet material so as
to form a backing.
Preferably said fibrous material is cardboard.
The flexible linear charge system as herein described and with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described with
reference to the accompanying drawings wherein:
FIGS. 1A to 1L are cross sectional views of a variety of elongate
shaped explosive charge elements according to a first embodiment of
the invention.
FIGS. 2A to 2E are cross sectional views of a variety of elongate
shaped explosive charge elements according to a second embodiment
of the invention.
FIG. 3 is a rear elevation view of a first embodiment of a charge
carrier according to the invention.
FIG. 4 is a side elevation of the charge carrier of FIG. 3.
FIG. 5 is a cross sectional view of a member of the charge carrier
of FIG. 3.
FIG. 6 is a cross sectional view of the member of FIG. 5 with an
elongate shaped explosive charge element installed.
FIG. 7 is a rear elevation view and side view of a second charge
carrier according to the invention.
FIG. 8 is a cross sectional view of the charge carrier of FIG.
7.
FIG. 9 is a front, side and end view of a loading card according to
the invention.
FIG. 10 is a detail elevation and plan view of a filling end cap of
the charge carrier of FIG. 7.
FIG. 11 is a sectioned perspective view of a linear charge
system.
FIG. 12 is a diagramatic, not to scale, representation of a
sectioned perspective view of a linear shaped charge element.
FIG. 13 is a diagramatic, not to scale, representation of a section
of a further preferred linear charge element.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In accordance with a first embodiment of a forced entry system, a
principle component in this instance of which is a flexible
frangible cutting sheet intended for use with explosive charges to
cut through obstructing material. The structure of this sheet is
made up of a polymer matrix including plasticisers, stabilizers and
flexible agents, containing a substantially uniform distribution of
powdered metal. The metal may be any one of a selection of metals
including for example, copper, aluminium, brass, ferrous metals,
ceramics or a combination of these.
Preferably the particulate size of the metal or ceramic powder is
in the order of 1 to 10 microns but both smaller and larger
particles may be used. Different combinations of sheet thickness,
particle density and particle size may be formulated depending on
the explosive charge to be used and the nature of the barrier
structure to be penetrated. That structure may comprise a wide
range of materials including wood, metal, masonry, glass,
polycarbonates and other plastics as well as composites.
The flexible nature of the cutting sheet enables it to be combined
into a variety of elongate shaped charges when provided with an
explosive agent. Desired shapes may also be achieved by extrusion,
casting or fabricating.
By suitable shaping and the use of a stand-off material the cutting
sheet may be adapted to take advantage of the "Monroe Effect"
wherein the detonation of the explosive agent creates a high energy
linear jet of gas. The stand-off material serves to provide that
distance between the explosive agent and the target required for
the accelerating gas and particles of the cutting sheet to reach an
effective penetration velocity. The stand-off material may be made
of any light frangible material such as for example a polystyrene
foam.
FIGS. 1A to 1L show a number of examples of preferred
configurations of a cutting sheet (2), stand-off material (1) and
explosive agent (3). As shown for example in FIGS. 1A, 1C, 1G, 1H,
1I and 1J, an additional layer of flexible frangible cutting sheet
(2) may be incorporated as a tamping layer.
It is a feature of the flexible frangible cutting sheet that the
individual particles accelerated by the blast are of very low mass
and thus lose energy rapidly from their initial high energy state
after detonation of the explosive agent. As a result their
penetration effect is limited to a very short range, thus
minimizing fragmentation and the likelihood of unintended injury to
any persons within the structure to be penetrated.
In an extruded form, the flexible frangible cutting sheet may be
backed with a sheet explosive agent to obtain the desired cutting
effect. Furthermore, extruded forms may be placed in a carrier
adapted to incorporate a fluid tamping means, as is further set out
below.
In a second preferred embodiment of the invention, the flexible
frangible cutting sheet is itself loaded with an explosive charge
to produce a flexible frangible explosive cutting sheet. As with
the first embodiment this sheet may be formed by a variety of means
including extrusion, casting and fabrication, and may be shaped and
combined with a suitable stand-off material to produce a "Munroe
Effect" discharge when detonated.
In a third preferred embodiment of the invention, either the
flexible frangible cutting sheet or the flexible frangible
explosive cutting sheet, may be combined in a variety of
configurations with explosive agents and a metal liner, as shown in
FIG. 2 in which (2) is a layer of flexible frangible cutting sheet
or flexible frangible explosive cutting sheet, (3) is an explosive
agent, (1) is a stand-off material and (4) is the metal liner.
In this embodiment it is the metal liner which acts as the cutting
or penetrating agent with the cutting sheet providing a tamping
effect and aiding the shaping of the "Monroe Effect".
All the embodiments of explosive charges described above may be
used alone by direct application to the surface to be penetrated,
or as charge elements of charge carriers according to the
invention.
A first preferred embodiment of a charge carrier (10) particularly
adapted to the penetration of masonry walls, including single,
double and cavity brick walls, concrete block walls and light
formed concrete walls, is shown in FIGS. 3 and 4. A perimeter frame
(11) is formed of polymeric hollow section and includes at least
one cross member (12). Carrier perimeter frame (11) is further
provided with carry handles (13) and a telescopically adjustable
hinged support brace (14). Height adjustment of the frame may be
provided by means of foot elements (15) sliding in sleeves (16) and
located at a preferred height by locking pegs (17) passing through
a plurality of holes (18) in sleeves (16).
Arranged at intervals on the rear face (19) of frame (11), that is
that face directed away from the masonry wall to be penetrated, is
a plurality of charging ports (20) to allow for detonation of the
explosive charge elements carried by the frame.
One preferred sectional shape of a perimeter frame (11) and cross
member (12) is shown in FIG. 5. The front face (21) of the extruded
sections, that is the face directed towards the object to be
penetrated, is shaped with a holding channel (22) adapted to
receive as a snap-fit pre-formed elongate charge elements of either
the flexible frangible cutting sheet or the flexible frangible
explosive cutting sheet type as described above. The frame members
may be extruded in a variety of cross sectional shapes and charge
holding cavities to suit various operational conditions and charge
element shapes.
Again with reference to FIGS. 3 and 4, frame (11) is sealed and is
provided with filler ports (23) and closure caps (24) allowing the
frame to be filled with a tamping agent such as water. Optionally,
frame (11) may be prepared at manufacture with a gelling agent so
as to create a gel when the frame is filled with water to prevent
leakage in the case of accidental fracture of the frame in an
operational situation.
The frame charge element holding cavity (22) is preferably so
configured as to obviate the need for the charge element to be
provided with stand-off material; the required stand-off distance
being provided by the frame itself as shown for example in FIG. 6.
Here an elongate shaped charge (25) comprising flexible frangible
cutting sheet (26) and explosive agent (27) has been fitted to
cavity (22).
In a second preferred embodiment of a charge carrier according to
the invention as shown in FIG. 7, carrier 100 is adapted to effect
a directed explosive charge in which water or other fluid acts as
the penetrating agent. This second preferred embodiment is adapted
in particular to any of a variety of door constructions, including
commercial or domestic metal roller doors, metal doors, fire doors,
reinforced timber doors and glass doors. It may also be used for
some wall structures.
As shown in FIG. 7, charge carrier (100) has a main body (101)
preferably formed of an extruded polymer section (as can best be
seen in FIG. 8), although it may also be formed as a casting or
fabrication. The composition of the polymeric barrier body (101)
may include plasticisers to reduce brittleness. The carrier body
(101) may be of any desired length depending on the intended
application but is preferably in the range of 1.2 to 1.8 meters.
Although a rectangular section is preferred, the body (101) may be
square, triangular, oval or circular.
As shown in FIG. 8, the internal side walls (102) of body (101) are
provided with guide rail elements (103). Body (101) is sealed at a
first end (104) with a sealing end cap (105) and provided with a
filler end cap (106) for closure at a second end (107). Filler end
cap (106) is further provided with a filling port closure cap (108)
and a detonating cord grommet (109) as shown more clearly in FIG.
10.
Sealing end cap (105) may be permanently assembled to body (101)
during manufacture, while filler end cap (105) remains detachable
until the carrier is prepared for use at a detonation site.
Alternatively, both end caps may be supplied loose so as to allow
detonation access to both ends of the carrier body.
Carrier body (101) may further be provided with an adjustable foot
portion (110) to allow for height adjustment and a telescopically
adjustable hinged support brace (111). Adjustable foot portion
(110) may be formed of a sleeve of larger section than the sealing
end cap (105) and be provided with a plurality of adjustment holes
(112) for the insertion of suitable locking pegs (113).
Additionally, carrier body (101) may be fitted with flexible
magnetic strips (114) so as to allow for its attachment to metal
surfaces.
Guide rail elements (103) are adapted to locate an explosive
loading charge (120). In a first form as shown in. FIG. 9, the
loading charge (120) is comprised of a loading card (121) and
detonating cord (not shown) Preferably, loading card (121) is in
the form of a rectangular sectioned extruded polymer slat having
front and rear wall portions (122) and (123) with a plurality of
transverse divider portions (124) so as to form a number of
longitudinal passages (125) between the two wall portions, as shown
in FIG. 8. The thickness of the card is such as to mate as a
friction fit in rail elements (103). In one preferred form of the
card (120) as shown in FIG. 9 the outer ends of the card are
provided with slots (126) and holes (127) coinciding with passages
(125).
In this form a desired length of detonating cord may be installed
as lying along the face of the front wall portion (123) of the
card, looping through the slots and holes so as to locate the cord
to the card. Alternatively, the detonating cord may be threaded
through the passages (125) and so winding about the front wall
portion (122).
In use, a length of loading card is prepared with a length of
detonating cord, lengths of both card and detonating cord selected
according to the expected force required to achieve penetration,
and inserted into the guide rail elements (103). The detonating
cord is passed through the grommet (109) of the filler end cap 106
and the cap assembled to the carrier body (101), for example by the
use of a suitable adhesive.
The carrier body can now be filled with a tamping fluid.
Optionally, the carrier body (101) may be prepared with a lining of
a suitable gelling agent so that when filled, the fluid forms into
a gel thus preventing leakage of the tamping fluid in the event of
accidental fracturing of the carrier body, or lternativley a
gelling agent may be added with the water. When detonated, the
charge on the loading card, explosively accelerates the tamping
fluid through the carrier body and into the target other tamping
agents than water may be used such as sand or soil. These agents
can be readily introduced into the charge body through the large
filling port.
The effectiveness of the penetrating operation of the second charge
carrier embodiment may be enhanced by the placement of a flexible
frangible cutting sheet In front of the detonating cords, or
alternatively, replacing the detonating cord with a flexible
frangible explosive cutting sheet. This sheet may be attached to
the loading card by adhesive tape, for example or be adapted to
slide into slide rails between the loading card and the target side
of the charge carrier.
This second embodiment of a charge carrier according to the
invention described above is particularly suited to the forced
entry of doorways where there is a perceived asymmetry of strength
in the door structure. Thus for example in a roller door situation,
the charge is effective in urging that side of the door from its
guide rail when the carrier body is aligned adjacent to an edge of
the roller door.
An advantage of the present embodiment is that the flexibility of
the system allows it to be prepared, if required, on-site to suit a
wide range of forced entry requirements.
The carrier is designed so that the explosive charge can be tamped
in a number of different ways. It can be located to act as an
outright fracturing charge to take advantage of the brisance of the
explosive detonation. Alternatively as indicated above, the charge
can be sandwiched between layers of tamping material. In this
configuration the tamping layer away from the target acts as a
tamping agent, increasing the effectiveness of the explosive effect
and minimizing overpressure effects. The side towards the target
conveys explosive energy into the target material. Water, or gelled
water is the optimum tamping material, offering excellent
confinement with no shrapnel concerns.
The loading card can be pre-assembled with the explosive load. It
then takes only moments to prepare the charge carrier. An advantage
of the separate loading card is that only it needs be stored in an
explosive magazine; the other components may be stored in any
convenient way. Various loading cards of different lengths and with
varying explosive loads may be pre-assembled and stored in
anticipation of use.
Alternatively, in a third preferred embodiment of a charge carrier,
the components to make up a charge carrier are provided in a
disassembled kit form. The kit then includes at least one length or
a selection of lengths of polymer extrusion, a matching length or
lengths of loading card, a sealing end cap and a filler end cap, as
well as sufficient length of detonating cord and gelling agent. The
sealing end cap may be pre-assembled to the carrier body but an
alternative form of the kit may be supplied with two loose filler
end caps thus allowing two or more charge carriers to be linked
together into one explosive charge assembly.
In addition the kit may be provided with a roll of double sided
adhesive tape to allow the charge carrier body to be directly
attached to a surface. Where adhesion is not possible because of
the nature of the surface, a support structure may be included in
the kit in the form of the adjustable foot portion and hinged
support brace as described above.
In at least one preferred form of this embodiment sealing end cap
and filler end cap may be provided with projecting lifting or
attachment lugs 130 as shown in FIG. 10 for the attachment of
carrying slings or as an aid to securing the charge carrier in a
location for use.
In yet a further embodiment of the invention as shown in FIG. 11, a
linear charge system is provided in the form of a flexible elongate
member 140 incorporating a malleable, in this example chevron
shaped explosive 141, a liner 142 and a stand-off member 143, all
held in the matrix of an inertial mass tamping carapace 144. The
stand-off carcass may be in the form of a elongate flexible
closed-cell foam structure or an extruded flexible hollow tubular
member (as shown in FIG. 11).
In at least one preferred form of this embodiment the elongate
member 140 may be provided with contact adhesive strips 145 along
its underside or with flexible magnetic strips for retaining the
elongate member against a surface to which the charge is to be
applied.
As can be seen in FIG. 11 the inertial mass tamping carapace in
cross section completely envelops the explosive 141 and liner 142
elements as well as the stand-off member 143 except for the gap 146
at its underside. This gap 146 is to allow the focussed passage of
the high energy linear jet of gas and particles of the
explosive.
The liner 142 is in the form of a separately extruded plastic
matrix incorporating an extremely dense distribution of metal
carbide as the main liner ingredient. This allows the generation of
a high velocity, high density, extremely abrasive jet with superior
penetrative performance.
The malleable explosive may be any readily available commercial
sheet explosive with sufficient flexibility and an adequate
detonation velocity. Exemplary products are Ensign Bickford
Primasheet 2000, Dyno HLX sheet explosive, Royal Ordnance SX2 sheet
explosive or Royal Ordnance Demex 200. All have adequate physical
properties and velocity of detonation above 7600 metres/second,
which is sufficient to enable efficient liner jetting.
The addition of a dense, non toxic, flexible, plasticized metal
composite mass tamping carapace over the explosive chevron enables
the detonation of the explosive to be effectively tamped at the
detonation instant, thus focusing more detonation energy to
effectively collapse and accelerate the liner into an effective
penetrating jet. The mass tamping carapace may be composed of a
dense inert compound, for example powdered barium sulphate or other
dense non-toxic metal or metal compound and plasticizer on
detonation the carapace disintegrates as a cloud of fine particles,
with a very small lethal or injurious radius compared to totally
metal enclosed linear shaped charges.
A tubular stand off member may optionally be pressurized for
underwater use by the addition of elastomer bungs at the ends of
the tube, one of which at least may be provided with one way valve
means to introduce and retain a gas under the required pressure.
This system has advantages over a comparable closed cell foam stand
off which will gradually compress as the gas filled bubbles in the
foam contract with increased water pressure, thus reducing the
optimum stand off that a linear shaped charge needs for adequate
cutting performance.
Since a gas filled pressurized tubular support is better able to
withstand water pressure it enables the liner to jet with more
effect into the target and without the jet degrading by passage
through foam.
Although the present embodiment has made reference to a chevron
shaped explosive charge, it will be clear to a person skilled in
the art that any shape inducive of producing a "Monroe Effect",
such as for example an arcuate sectional shape or an arrangement in
a number of segments may also be effectively employed.
The present embodiment may be pre-assembled for "off-the-shelf"
availability in a number of configurations to suit a variety of
commonly encountered requirements. Alternatively, it may be
provided in kit form. The kit may include one or a number of
standard lengths of closed cell foam or open tubular stand-off
carcass, and a quantity of pre-cut sheet explosive so as to enable
a user to assemble a desired thickness on-site. The kit would also
contain an appropriate length or lengths of liner of nominated
properties and composition as well as one or more lengths of
tamping carapace produced in a form allowing insertion of the
explosive, liner and carcass components. Accessories, such as
adhesive or magnetic strips, closing bungs and adhesives to fix
them in place, and a hand pressurization pump for example, may also
be provided.
In yet a further preferred embodiment of the invention as shown in
FIG. 12 a linear shaped charge element 200 is formed of an extruded
carcass 210 of closed cell foam having a hollow tubular center 211.
The carcass has side flange portions 212 and 213 which form
termination elements for a first overlaid layer 214 of a composite
liner material, a second overlaid layer 215 of explosive sheet and
a third overlaid layer 216 of an inertial mass tamping carapace.
Both layers are affixed to the carcass 210 by a suitable adhesive.
Preferably, the liner material is formed of tungsten carbide
particulates in a flexible plastic matrix.
The underside 217 of the linear shaped charge element may be
provided with an adhesive layer 218 so as to allow the charge to be
applied to any suitable surface. The flexible nature of this
embodiment allows of its application to complex curved surfaces,
such as for example to circular section pylons, steel tanks and
even the surfaces of vessels for example.
In a further preferred embodiment of a linear charge element 300 as
shown in FIG. 13, a section of explosive sheet 311 is affixed to a
plastic carrier 310 in the form of a portion of a plastic tube such
as for example PVC pipe. In this embodiment the explosive charge
covered by a layer of cardboard backing 312.
The above describes only some embodiments of the present invention
and modifications, obvious to those skilled in the art, can be made
thereto without departing from the scope and spirit of the
invention.
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